It looks like you are anaemic. If you have back pain
after you sit for long hours then it is due to your haemoglobin levels as it is important to check that. Anaemia always leads to the symptoms of being tired and also having back / leg pain
though there may not be any pathological reasons for back pain
. The lower end of the vertebral column is inflamed and that bone is called coccyx bone and the condition is called Coccydynia. The conservative management would be to keep ice in that inflamed area during one time in a day and also to sit in a hot water bowl where the penetration of the heat would help to reduce the inflammation. And to reduce the weight falling on the inflammed surface we suggest patients to use air cushion pillow (also called as doughnut pillow) where in the buttock's weight will not fall exactly on the painful tail bone and that would automatically reduce the pain.